Italy's government is ready to pump 15 billion euros into Monte dei Paschi di Siena and other ailing banks, sources said, as the country's third-largest lender pushes ahead with a private rescue plan that is widely expected to fail.

The world's oldest bank has until Dec. 31 to raise 5 billion euros ($5.2 billion) in equity or face being wound down by the European Central Bank, potentially triggering a wider banking and political crisis in Italy.

If needed, the government will pump 15 billion euros into the Siena-based lender and several other smaller banks to prevent that, two sources close to the matter said on Thursday.

One source said unlisted regional banks Banca Popolare di Vicenza and Veneto Banca, which were rescued this year by a state-backed fund, would also get support from the state.

The government would make the 15 billion euros available in a decree on Dec. 22, La Repubblica newspaper said on Thursday, adding that Banca Carige could also benefit.

Italy's banking sector is saddled with 356 billion euros of bad loans, around a third of the euro zone's total and a legacy of the 2008-2009 global financial crisis when, unlike Spain or Ireland, Italy did not act to help its banks.

Fee negotiation

The JPMorgan-led plan calls for Monte dei Paschi to raise 5 billion euros in equity through a share sale and an offer for holders of its subordinated bonds to convert them into shares.

Monte dei Paschi is in the process of renegotiating fees with JPMorgan and the other banks that will try to sell the bank's stock after they walked out of a deal to underwrite the share issue, sources have said. Back in October, its CEO Marco Morelli had said that commissions for the cash call would only be paid in case of success.

Monte dei Paschi said on Thursday that 65 percent of the share sale would be reserved for institutional investors. It would also extend its debt-swap offer to include investors who hold 1 billion euros in hybrid securities known as "Fresh 2008".

It also wants retail investors to convert their subordinated bond-holdings, totalling 2.1 billion euros, into shares. Italian market watchdog Consob approved the offer late on Thursday, a source close to the matter said, paving the way for it to start as early as on Friday.

In a sign of doubts still surrounding the plan, Monte dei Paschi said it had set a range of one to 24.9 euros per share for the new equity. Even at 1 euro, the bank would be demanding a higher valuation than nearly all its domestic rivals.

Another source close to the matter also said Qatar's sovereign wealth fund, which bankers have said could invest 1 billion euros in the bank, had yet to make up its mind.

If Rome bails out the lender, European Union rules require that private investors share in its losses -- a politically dangerous condition for Italy's main ruling Democratic Party given early elections are looming next year.

Hundreds of thousands of ordinary Italians have invested in shares and bonds of local banks. A bailout of four small banks last year hit thousands of small savers.

Italy is in talks with the European Commission over ways to shield retail bondholders who would see their notes converted into shares in the event of a state bailout, sources have said.

As in the case of the four rescued banks, the Commission would allow the government to spare small bondholders only if they can prove they were victims of mis-selling and did not understand the risk in their investment, one source said.